Primary cardiac tumours are very rare,1 2 and when found incidentally during surgery and/or at unusual locations3 may require intraoperative frozen section diagnosis to decide on further management. During mitral valve repair operation in a 70-year-old man, a 5×5×1 mm gelatinous lesion was noted in the left atrium, attached to the wall and very close to the left upper pulmonary vein. While it had not been noted on preoperative echocardiography due to its small size, intraoperative frozen section diagnosis was asked in order to characterise this lesion.

Frozen section revealed a solid myxoid tumour with scanty cellularity comprising few round to oval cells admixed with what looked like blood vessels, consistent with cardiac myxoma (fig 1A, B). The base was free of tumour indicating complete excision. On paraffin sections, this …